Fluid meter



Jan. 17, 1950 E. F. STOVER 2,494,731

FLUID METER Filed Sept. 29, 1944 2 Sheets-Sheet 1 1 1/1 fimwamtow:

E wfiiwarzfi Sawyer Jan. 17, 1950 E. F. STOVER 2,494,731

FLUID METER Filed Sept. 29, 1944 2 Sheets-Sheet 2 1 1L 1 7 /6 l H} 3+Farce in be measured Jnvenfior: Emmy/Wank AS'z'o We? Patented Jan. 17,1950 UNITED STATES PATENT OFFICE FLUID METER Emory Frank Stovcr,Wynnewood, Pa.

Application September 29, 1944, Serial No. 556,378

25 Claims. (Cl. 73-205) My invention relates to/improvements in ameasuring system for measuring and indicating variations in conditionsand forces, where it is desired to obtain a square root relation of theforce to be measured.

My invention particularly relates to flow meters used in connection withprimary metering devices, such as Venturi tubes, orifices, nozzles andPitot tubes, connected in conduim, or with Pitot tubes used forobtaining the speed of ships, aeroplanes, or the like. and adapted forobtaining a differential pressure, or force, proportional to the squareof flow, or speed.

The object of my invention is to provide a novel measuring system forobtaining the square root relation of a differential pressure or force.

A further object is to provide a measuring system having a source offluid pressure supply. preferably air, and hereinafter termed a pilotfluid, which is separate and independent of the flow of fluid through aconduit, and provide apparatus for controlling the flow of the pilotfluid for obtaining a measurement of a condition, force, or therate offlow of fluid.

A further object is to provide means in the form of a tube for producinga laminar flow of the pilot fluid through a given length of the tube. inwhich the pressure drop resulting from the laminar flow through the tubeis directly proportional to the velocity through the tube.

A further object is to provide indicating means, in the form of a gauge,for indicating the first power or the velocity of the pilot fluidthrough the laminar flow tube, and provide a plurality of connectionsbetween the tube and the gauge by which the efiective length of the tubemay be varied.

A further object is to employ an impact, or Pitot tube, against whichthe discharge from the laminar flow tube is applied for producing astatic pressure within a pressure responsive device, which pressure isproportional to the square of the rate of flow through the laminar flowtube.

A further object is to provide apparatus for opposing the movement ofthe pressure responsive device by a force to be measured.

A further object is to provide means actuated by the movements of theresponsive device for varying the supply of the pilot fluid, to thelaminar flow tube, for maintaining the responsive de- 2 will show areading directly proportional to said initial force.

A further object is to provide a meter for measuring the flow of fluidthrough a conduit, in which meter the velocity of the pilot fluid, asshown by the reading of the gauge, will be directly proportional to therate of flow through the conduit.

A further object is to provide apparatus including a lever, for opposinga differential pressure produced by a primary metering device connectedin the conduit, by the force produced by the Velocity of the pilotfluid, and provide means for adjusting the ratio of the arms of thelever for adapting the apparatus to different maximum rates of flow inthe conduit.

These together with various other novel teatures of construction andarrangement of the parts, which will be hereinafter more fully describedand claimed, constitute my invention.

Referring to the accompanying drawings:

Fig. 1 is a central vertical sectional view of a flow meter embodying myinvention.

Fig. 2 is a horizontal section on line 2-2, Fig. 1.

Fig. 3 is a transverse vertical section on lines 3-4, Fi s. 1 and 2.

Fig. 4 is a diagrammatic view of a measuring system illustrating theoperation of the laminar flow tube and parts associated therewith.

In the drawings in which like reference characters refer to like parts,5 represents a flow meter comprising a base 6, upon which is securedlongitudinal side frame members I and 8, secured to said base by screws9. A differential pressure responsive device l0, comprising a. casingi2. is secured to the frame members 1 and I by screws III. A secondpressure responsive device ll, comprising a casing I5, is secured tosaid frame members by screws IS.

A lever I1 is pivoted upon the frame members 1 and 8 by means of a knifeedge cross-bar l8, rigidly secured in a head l9, which in turn isadjustably secured upon the lever H by a thumb screw 20, which permitsthe head I 9 to be adjusted relatively to the lever l1 and the cross- Ibar to be adjusted longitudinally upon the memhers I and 8, for varyingthe position of the fulcrum relatively to the arms of the lever l7. Saidlever ll is also provided with a movable counter weight 2 I.

The differential pressure device H1 is provided with a flexiblediaphragm 22 forming a high pressure chamber 23 and a low pressurechamber 24. The diaphragm 22 is secured between clamp plates 25 and 26and a rod 21 is secured to said clamp plates and is movable with thediaphragm. The rod 21 has a head 28 formed with cheek plates 29 whichstraddle the lever ll. Said cheek plates 29 are provided with apertures30 adapted to embrace a knife edge cross-bar 3|, secured s earer uponthe lever rod. 21} is slidably mounted in saunas boxes 22 and 33 uponthe casing l2, forming the responsive device it.

A primary metering device, in the form of a "Venturi tube 35, isconnected in a conduit 36, for measuring the rate of flow of fluidthrough the conduit 36. The primary device 35 is connected by a pipe 38with-the high pressure chamber 23 and by a pipe 39 with the low pressurechamber 24, of the responsive device ID. A differential pressure is thusapplied to the diaphragm 22, the action of said pressure is applied tothe rod 21, and to the knife edge 3!, secured upon the arm l'la of thelever [1. The differential pressure applied to the diaphragm 22 isproportional to the square of the rate of flow through the conduit 36.

The pressure responsive device l4 has a flexible diaphragm 40, forming apresure chamber 4!, within the casing l5. The diaphragm 40 is securedbetween clamp plates 42 and 43 by means of a shaft 44. The shaft 44extends without the chamber 4| and engages a knife edge 45, upon the armNb of the lever 11. The shaft 44 is provided with a screw thread adaptedfor adjustably securing the shaft upon the clamp plates 42 and 43 andthe diaphragm 40. By this construction an adjustment may be made betweenthe diaphragm and the lever l1.

An impact, or Pitot tube, 50 is mounted upon the casing l andcommunicates with the chamber 41 through a passage 5|, formed throughthe tube. Said tube 50 consists of a short threaded sleeve secured inthe casing i5 and adapted for clamping a bracket 52 upon the casing bymeans of a clamp nut 53. Said tube 50 has an inlet end 54 open to theatmosphere.

A laminar flow tube 55, having a' passage 55,

is secured by nuts 51 and 58 upon the bracket 52, in axial alignmentwith the Pitot tube 50. The discharge end 53 of the tube 55 is mountedin spaced relation with the inlet end 54 of the tube 50, and forms a gap60 between the tubes 50 and 55. When air is projected from the tube 55against the impact end of the tube 50 a pressure will be created withinthe chamber 4|, as hereinafter more fully explained.

The laminar flow tube 55 is provided with a screw threaded portion whichis in slidable engagement with the bracket 52, whereby the gap 60 may bevaried and the tube 55 secured in an adjusted position upon the bracket52 by the nuts 51 and 58.

The laminar flow tube 55 is connected with a valve casing 62, throughwhich the pilot' fluid, such as air, under the pressure, is suppliedthrough a pipe $3 from a source of supply. A valve 64 is adapted toengage a valve seat 55, formed upon the casing 52, and controls the flowof air to the laminar flow tube 55.

A rod 56 is mounted for movement upon the axis or the laminar flow tube55 and also upon the axis of the Pitot tube 50 and is adapted foroperating the valve 54 when the rod is actuated by the diaphragm 40, towhich said rod is secured.

Said rod 65 is also adapted for reducing the radial width of the annularpassage 56, through the laminar flow tube, to the proper size formaintaining laminar flow.

The rod 66 is rigidly secured to the shaft 44, which in turn is rigidlysecured to the diaphragm 40. The opposite end of the rod 66 is providedwith a threaded portion 68, which provides means for adjusting the valve64 upon said rod and relatively to the valve seat 85.

' tube .55 againstthe impact end 54 of the tube 5t creates a staticpressure within the chamber 46, which pressure is proportional to thesquare of the velocity of the air impinging upon the tube 50.

When there is a flow of fluid through the conduit 36. a differentialpressure in the responsive device In will cause the diaphragm 22 toactuate the lever l1, and the lever will move the rod 68 and hold thevalve 84 open until the flow of air, or pilot fluid, through the laminarflow tube 55 increases thev pressure within the chamber 4| suflicientlyto balance the lever ll between the pressures acting upon the diaphragms22 and 40; the lever I! will then actuate the valve 54 for supplying therequired flow of the pilot fluid to maintain the lever I! in balancebetween the forces acting upon the diaphragms 22 and 40.

A gauge 10 is adapted to be connected with the laminar flow tube 55, atvarious points throughout the length of the latter, by means of pipes H,12, I3 and 14, each pipe being provided with a valve 15. By closing allbut one of said valves 15 the effective length of the laminar flow tube55 may be varied to accommodate the limiting deflection of the gauge Illto different limiting rates of flow through the primary metering device35.

The fulcrum I! of the lever ll may be varied for changing the ratio ofthe lever arms Ila and 11b by adjusting the position of the block l9,upon the lever l1, and also upon the frame members 1 and 8. By adjustingthe ratio of the lever arms the maximum deflection of the gauge 10 canbe adjusted to the maximum flow through the conduit 35.

The adjustment of the tube 55, by means 01 the bracket 52 and the nuts51 and 53, relatively to the impact tube 50, provides means for adaptingthe tube 55 to primary devices 55 having coefllcients which vary withthe rate of flow through the conduit 35.

The principle upon which a tube having laminar flow operates isillustrated in Fig. 4, in which a laminar flow tube 55' is provided withan inlet connection 63', through which a fluid, preferably air, isadmitted. A gauge 10' is connected in communication with the tube,55',adjacent to the inlet end of the latter, by a pipe H, and is adapted forindicating the pressure drop in the length L1 between the pipe II' andthe discharge end 59' of the tube 55'.

An impact, or Pitot tube 50' is mounted with its open end adjacent toand in spaced relation with the discharge end of the tube 55'. A gaugeis connected in communication with the tube 50.

If a fluid is made to flow through the laminar 6 in which: athanyalmovemnt oi the diaphragm wig l ac ev vecon olmechanismiorregulag5; ffffiff: f a m; the supply 01 fluid to the laminar flow tubeL=the1ength of the until the diaphragm is balanced between the v=theaverage v 61 my. t g ittlrgzeorbzlr neasured and the pressure within theg: 22 2 332 8; 33%; a The laminar flow through the laminar ilow tube humdmmetertof the tube ll is discharged against the impact. or Pitot tube iII and produces a static pressure within the Reynolds number is thecriterion for deterin chamber ll which is proportional to the squaremining Whether the flow r u h acircular tube of said flow. When thediaphragm is in equilibri- W be a n turbulent, and this num um betweenthe pressure within the chamber 4! must be kept below 2000 to insurelaminar flow. and the force to be measured, the gauge 10' will Th y berepresented in h f l wing indicate the square root of the force to bemeasequation: u ea.

The gauges II and 'II' are oi'standard con- R.= H struction, havingequal increments of deflection ior equal increments of pressure, andwill indim which: v cate the square root or the force to be measured ona scale of uniform divisions. sl i fizgg xfia m The meter illustrated inFigs. 1 to 3, embodies d=the diameter of the tubethe above describedprinciples. In Fig. 1 the flow J=the mass density of the fluid. throughthe Venturi tube 35 and the conduit 00. H=the absolute viscosityartistes: differential pressure in the responsive e ce mm r fl w is e ni l to he operation f u If this diflerential pressure is termed ha, andq my inventmn- If the 110w lamina! the represents the rate of flowthrough the conduit pressure loss is proportional to about the second36, then: power or the velocity and it is also a function of theroughness of the tube. w

Referring to Fig. 4, if the tube II is constructed according to thenecessary restrictions 523??? the pressure of the pilot mud on the as tothe value of Reynoid's number, and a fluid is fed into the tube at theinlet at and ffgji ff g fifi chamber ejected at the outlet 50', thepressure drop on the length L1 will be proportional to the first powerK2 and K3 represent constants" of the velocity of t fluid through t t Itthe iorce from h: is balanced against the and the pressure drop will beindicated upon 1010B 3 then! the gauge I l. t

The fluid from the discharge end 50' of the 40 laminar flow tube 55' isdirected against the ma e, i

open end of the Pitot tube with an impact which will create a staticpressure within the i tube to and the chamber II, which is propor- -K'gtional to the second power of the velocity of the fluid impinging uponthe open end of the Pitot Kmmq tube It and the gauge" will indicate apressure 1 aq proportional to the square 01' ttlifnveloctthy in the Kqlaminar flow tube The rea g on e gauge is therefore always proportionalto the square Therefore the Rodin! i on he g uge III is diof the readingon the gauge II. At zero flow the 50 P Wm the rate f flow (1 throu hreading of the gauges l0 and II will be equal. the Primary device in theconduit 36.

, When there is a flow of fluid through the tube In 1 the tube and therod 55 f rm an an- 5I, and h represents the of gauge "I" passage alaminar and h: the reading of the gauge 00, and K1 reprec n bemaintained. This construction perm.ts

v the use of a tube II of large diameter, through 2?? a constant which apassage of uniform diameter throughout en. its entire length may beconstructed and the rod h,=K /E "may be constructed with a uniformdiameter having the proper cross-section to reduce the an- 3 00 nularspace It to the proper radial width to insure a laminar flow through thetube 55.

The measuring system illustrated in Fig. 4, in- The operation of themeter shown in Figs. 1 to cludes a chamber ll having a responsive wall,or 3 is as follower diaphragm 40''. The pressure created in the PitotThe meter is for measuring the rate of ilow of tube 50' is admitted tothe chamber ll and tends '65 fluid q through the conduit 30. The Venturitube to distend the diaphragm against a force to be II produces adifferential pressure In which is apmeasured. plied to the diaphragm,which latter produces A valve 84' is provided for controlling the supaforce through the rod 21 to the lever arm Ila, plyof fluid to thelaminar flow tube It. An arm which is proportional to the square of theflow q. 02, adapted for operating the valve, is connected (0 A downwardforce from the diaphragm 40, actby a rod 83, with one end of a lever 84.The oping through the shaft 44 upon the lever arm llb', posite end orthe lever is pivotally connected with opposes the force acting upon thearm I la. l a shaft 44', having one end thereof secured to If the twoforces acting upon the lever ii are the diaphragm and its opposite andadapted for not in balance, the rod 86 will operate the valve theapplication oi the force to be measured, as in- 75 l4 and vary the flowoi air, termed the pilot fluid.

The flow of the pilot fluid impinges upon the open end of the Pitot tubeEl and produces a static pressure in the chamber ll which will balancethe force acting at the knife edge 4! of the lever II. If the forceacting upon the lever H, at the knife edge 45, is not in balance withthe force acting upon the knife edge ll of the lever II, the diaphragm40 will move the rod 68 which in turn will move the valve 64 to or fromits seat and regulate the flow of the pilot fluid for maintaining thelever l1 balanced between the two forces.

The rod 66 is provided with a disk 85 which slides freely in the bore ofthe valve casing G2 and is adapted for holding the rod 66 centered uponthe axis of the tube 55, when the valve 64 is raised from its seat 65.

The gauge!!! will indicate the rate of flow of the pilot fluid throughthe laminar flow tube 55 which is required to maintain the forces actingupon the lever I! in balance and the gauge 10, being graduated in theproper units, will give a direct indication, at any instant, of the rateof flow of the fluid through the primary metering device 35.

I claim:

1. A meter comprising a tube adapted for producing laminar flow of fluidand for producing a friction loss which is a first power function ofsaid flow, means for controlling the delivery of fluid to said tube,means actuated by the flow of said fluid through the tube for producinga pressure proportional to the square of said flow, means for opposingsaid pressure by a force to be measured, and separate fluid pressureresponsive means connected to said tube for measuring the friction lossthrough said tube.

2. A meter comprising a laminar flow tube, means for controlling thedelivery of fluid to said laminar flow tube, an expansible chamber, animpact tube positioned adjacent to the discharge end of said laminarflow tube and in communication with said chamber, and means forsupplying fluid under pressure through said laminar flow tube anddischarging said fluid against said impact tube for producing a staticpressure within said chamber which is proportional to the square of thevelocity of flow through the laminar flow tube.

3. A meter comprising a laminar flow tube, separate means actuated bythe discharge of said fluid through the tube for producing a fluidpressure proportional to the square of said flow, means 8 said flrsttube, said pressure drop being a first power function of said velocity.

5. A meter comprising a Pitot tube, an expansible chamber incommunication with said tube, means for projecting a laminar flow offluid against the open end of said Pitot tube for pro- .ducing a staticpressure within said chamber which is proportional to the square of thevelocity of said laminar flow of fluid, and movable means responsive tothe pressure drop through said laminar flow means for producing aneffect proportional to the square root of the static pressure within thechamber.

6. A measuring system comprising a laminar flow tube, a Pitot tubepositioned adjacent to the discharge end of said first mentioned tube,means for producing a flow of fluid through said first tube forproducing static pressure within said Pitot tube, a structure responsiveto said static pressure and adapted to be opposed by a force to bemeasured, and means actuated by said structure adapted for varying therate of flow through said first tube for maintaining the forces act uponsaid structure in balance.

7. A measuring system comprising a laminar flow tube, a Pitot tubepositioned in spaced relation to the discharge end of said flrstmentioned tube, means adapted for varying the space between thedischarge end of said flrst tube and the inlet end of said Pitot tube,means for producing a flow of fluid through said flrst tube forproducing a static pressure within the Pitot tube, a structure foropposing the action of said fluid pressure by a force to be measured,fluid pressure responsive means connected to said tube for measuring therate of flow through said tube as an indication of the square root ofthe force to be measured, and means for controlling the delivery offluid to the laminar flow tube.

4. A meter comprising a source of fluid pressure supply, a tubeconstructed with a passage of the required cross-section for conductinga laminar flow of said fluid through a given length of said tube, meansfor controlling the delivery of fluid from said source to said tube, anexpansible chamber, a Pitot tube in communication with said chamberhaving an open end positioned in spaced relation to the discharge end ofthe first mentioned tube for receiving an impact of said fluid forproducing a static pressure within said chamber which is proportional tothe square of the velocity through said given length of the firstresponsive to said static pressure and adapted to be opposed by a forceto be measured, means actuated by said structure adapted for varying therate of flow through said flrst tube. and means for indicating the rateof flow through said first tube.

8. A measuring system comprising a source of fluid pressure supply, atube adapted for conducting said fluid with laminar flow through a givenlength of said tube, a chamber having an inlet opening positionedadjacent to the discharge end of said tube adapted to receive an impactof said fluid to produce a static pressure within said chamber which isproportional to the square of the velocity of the flow through saidtube, means actuated by said static pressure adapted for controlling thesupply of fluid to said tube, and means for indicating the rate of flowof fluid through said tube.

9. A measuring system comprising a laminar flow tube, means forsupplying fluid under pressure to the inlet end of said tube, a casingforming a static fluid pressure chamber, an impact tube communicatingwith said chamber having an open end subjected to the impact of fluiddischarged from said laminar tube, a yieldable member forming a wall ofsaid chamber responsive to said static pressure, means for applying aforce to be measured to said member opposing saio static pressure, andindicating means responsive to flow through said laminar tube.

10. A measuring system comprising a laminar flow tube, means forsupplying fluid under pressure to the inlet end of said tube, a casingforming a static fluid pressure chamber, an impact tube communicatingwith said chamber and having an open end'subiected to impact of fluidfrom saidlaminar tube, a yieldable member forming a wall of said chamberresponsive to pressure created by said impact, means for applying aforce to be measured to said member for opposing the action of saidstatic pressure, and means actuated by the movements of said member forvarying the s earer 9 supply of fluid to said laminar tube formaintaining the forces acting upon said member in balance.

11. A measuring system comprising a laminar flow tube of a given lengthfor producing a pressure drop which is a flrst power function of saidflow, separate means actuated by said laminar flow for producing astatic pressure proportional to the square of the velocity of said flow,a member mounted for movement responsive to said static pressure, meansfor applying a force to said member which is proportional to a force tobe measured and arranged for opposing the movement of said member bysaid static pressure, a

valve for varying the fluid supply to said tube, means responsive to themovements of said member adapted for actuating the valve for maintainingsaid member in balance between said static pressure and said force to bemeasured, and fluid pressure responsive means connected to said tube forindicating the rate of flow through said given length of said tube.

' 12. A measuring system comprising a tube constructed for conducting alaminar flow of fluid through a given length of said tube, means actu-'ated by said laminar flow for producing a static pressure proportionalto the square of the velocity of said flow, a member mounted formovement responsive to said static pressure, means for applying a forceto said member which is proportional to the square of a force to bemeasured and arranged for opposing the movements of said member by saidstatic pressure, a valve for varying the fluid supply to said tube, avalve rod operatively associated with said valve and responsive to themovements of said member adapted for actuating the valve for maintainingsaid member in balance between the static pressure and the force to bemeasured, means for adjusting the eflective length of said rod betweenthe valve and said member, and means for indicating the velocity of flowthrough the tube.

13. A measuring system comprising a source of fluid supply, a tubeconnected with said supply, a rod positioned coaxially within said tubeand forming a laminar flow passage through the tube for said fluid,means actuated by the flow of said fluid through the tube for producinga pressure proportional to the square of said flow, means for opposingsaid pressure by a force to be measured, and means for indicating thepressure drop through said tube.

14. A meter comprising a tube connected with l0 atively associating therod with the valve and with said structure for actuating the valve.

16. A measuring system comprising a tube connected with a source offluid supply, a valve located between the inlet end of said tube andsaid supply, a rod adapted for operating the valve for varying thesupply of fluid to said tube, said rod positioned coaxially within saidtube and forming a laminar flow passage through said tube for the fluid,a Pitot tube positioned in axial alignment with the flrst mentioned tubefor producing a static pressure within the Pitot tube by the dischargeof fluid from said flrst tube, a structure responsive to said staticpressure and adapted to be opposed by a force to be measured, said rodextending axially within the Pitot tube, and means mounting the rod formovement with said structure for actuating the valve.

17. A meter comprising a tube adapted for producing a laminar flow offluid and for producing a pressure drop which is a flrst power functionof said flow, means for controlling the delivery of fluid to said tube,means actuated by the discharge of said fluid from the tube forproducing a pressure proportional to the square of said flow, means foropposing the action of said pressure by a force proportional to thesquare of a source of fluid supply, a rod positioned coaxially withinsaid tube with'the adjacent surfaces of the tube and the rod in closerelation to each other to form a passage for insuring laminar flow ofthe fluid through said passage, an expansible chamber having a movablewall, a Pitot tube in communication with said chamber and positionedadjacent to the discharge end of the flrst mentioned tube for producinga static pressure within the chamber, and means for applying a force tobe measured against said wall inopposition to said static pressure.

15. A measuring system comprising a tube connected with a source offluid supply, a rod positioned coaxially within the tube and forming alaminar flow passage through the tube for said the supply of fluid tosaid tube, and means opera quantity to be measured, fluid pressureresponsive and measuring means connected to said tube and responsive tothe rate of flow through said device, a member mounted for movementwithin said device by pressures whose difference is a measuresubstantially proportional to the square of the rate of flow of fluid, asecond pressure device, a member mounted for movement within saidseconddevice, a laminar flow tube for conducting a pilot fluid, an impact tubecommunicating with said second device, means mounting the impact tubefor receiving the impact from the discharge of said. laminar flow tubefor producing a static pressure upon the member of said second deviceproportional to the square of the flow of the pilot fluid, meansinterposed between said members for opposing the movements of saidmembers, a valve adapted for controlling the supply of the pilot fluidto the laminar flow tube, means for actuating said valve to restore saidlast means to balanced condition, and movable means responsive to thepressure drop through the laminar flow tube.

19. A measuring system comprising a pressure device, a member mountedfor movement within said device by pressure whose difference is ameasure substantially proportional to the square oi the rate of flow offluid, a second pressure device, a member mounted for movement withinsaid second device, a laminar flow tube for conducting a pilot fluid, animpact tube communicating with said second device, means mounting theimpact tube for receiving the impact from the discharge of said laminarflow tube for producing a static pressure upon the member of said seconddevice proportional to the square of the rate of flow of said pilotfluid, a lever having opposed arms subjected respectively to the forceson said members, a valve adapted for controlling the supply of the pilotfluid to the. laminarflow tube, means actuated by the unbalancing of themoments on said lever of the forces acting upon saidmembers foractuating the valve to restore said moments to balance, and means forindicating the pressure drop through the laminar flow tube.

20. A measuring system comprising a pressure device, a member mountedfor movement within said device by pressures whose difference is ameasure proportional to the square of the rate of flow of fluid, asecond pressure device, a member mounted for movement within said seconddevice. a tube for providing a laminar flow or a pilot fluid, an impacttube communicating with said second device, means mounting the impacttube for receiving the impact from the discharge of the laminar flowtube for producing a static pressure upon the member of said seconddevice proportional to the square of the rate of flow of the pilotfluid, a lever having opposed arms subjected respectively to the forceson said members, a bearing upon which said lever is fulcrumed, means foradjusting said bearing for varying the relative lengths of said arms, avalve adapted for controlling the supply of the pilot fluid to thelaminar flow tube, and means actuated by the unbalancing of the momentson said lever of the forces acting upon said members for actuating thevalve to restore said moments to balance. 7

21. A measuring system comprising a primary metering device, adifferential pressure responsive device subjected to pressures whosediilerence is a measure substantially proportional to the square of therelative velocity of a fluid with respect to said primary device, alaminar flow tube for a pilot fluid for producing a friction loss whichis a first power function of the velocity of said flow, a secondpressure responsive device actuated by a pressure proportional to thesquare of the flow of the pilot fluid, means opposing the responsiveaction of said responsive devices against each other, means actuated bythe unbalancing of the opposing means for varying the delivery of thepilot fluid to said laminar flow tube for restoring said responsivemeans to balanced condition, and fluid pressure responsive meansconnected to said tube for indicating the rate of flow of the pilotfluid for obtaining a direct measure of said relative velocity actingupon said primary device.

22. A measuring system comprising a primary metering device, adifferential pressure responsive device subjected to pressures whosedifference is a measure substantially proportional to the square of therelative velocity of a fluid with respect to said primary device, alaminar flow tube, a separate source of a fluid supply connected withsaid tube, a second pressure responsive device, means actuated by saidlaminar flow through said tube for producing a static pressure upon saidsecond responsive device proportional to the square of the rate of flowof the fluid through said tube, means interposed between said devicesadapted for opposing the forces within said responsive devices, meansresponsive to the unbalancing of the forces acting upon said responsivedevices adapted forcontrolling the flow of fluid through said tube torestore balance, a gauge adapted for indicating the rate of flow througha given length of said tube which flow is directly proportional to saidrelative velocity, a plurality of valved connections arranged in spacedrelation throughout the length of said tube and communicating with thegauge and adapted for varying said given length of the tube toaccommodate the limiting deflection of the gauge to diflerent values ofsaid relative velocity.

23. A meter for measuring the flow of fluid through a conduit comprisinga diflerential pressure responsive device actuated by pressure producedby flow through the conduit, a. laminar flow tube adapted for flow of apilot fluid through a given length of said tube, a second pressureresponsive device actuated by pressure produced by the flow oi the pilotfluid through said tube. means for opposing the responsive action ofsaid devices against each other, means actuated by the unbalancing ofthe opposing means for varying the delivery of the pilot fluid to saidlam flow tube for restoring said responsive devices to balancedcondition, and means for indicating the pressure drop of the pilot fluidthrough said tube for obtaining a. direct measure of the flow throughthe conduit.

24. A meter having a conduit, a primary metering device in said conduit,a structure responsive to difl'erential pressure produced by saidprimary device proportional to the square of the rate, of flow of fluidthrough the conduit, a tube adapted for producing a laminar flow of apilot fluid, means actuated by the discharge of said laminar flowthrough said tube for producing a static pressure proportional to thesquare of said 1aminar flow, means for opposing the action of saiddifferential pressure by the action of said static pressure, meansactuated by the unbalancing of the actions of said pressures adapted forvarying.

said laminar flow through said tube, and indicating means responsive tothe rate 01 said laminar flow through said tube for directly indicatingthe rate of flow through the conduit.

25. A measuring system for measuring the flow of fluid through a conduitcomprising a primary metering device in said conduit, a pressureresponsive device actuated by said primary device, a second pressureresponsive device, means for opposing the responsive action of saidresponsive devices against each other, a Pitot tube communicating withsaid second device, a flexible diaphragm forming a wall of said seconddevice, a laminar flow tube positioned in axial alignment with the Pitottube, means mounting said laminar tube in spaced relation to said Pitottube for producing a static pressure within said second device, a valveadapted for controlling the supply of a pilot fluid to said laminartube, a rod attached to said diaphragm and extending through said Pitotand laminar tubes, means mounting the valve upon said rod for movementwith the diaphragm, and a gauge responsive to the pressure drop of thepilot fluid through said laminar tube adapted for directly indicatingthe rate of flow through the conduit.

EMORY FRANK STOVER.

REFERENCES CITED The following references are of record in the flle ofthis patent:

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